This invention addresses air pollution control as well as an apparatus and method of performing large scale chemistry for bleaching, enhancing chemical reactions, and pollution removal. Extensive research is being done worldwide to develop new, commercially viable methods for removing undesirable chemical species from air or from exhaust gases such as combustion exhausts, contaminated liquids, such as industrial process effluents, or biologically contaminated water, and contaminated surfaces. Among the approaches to addressing these needs are technologies employing electrical excitation of a gas phase. The principal technologies include excitation by thermal, reactive chemical/catalytic, and non-thermal electric discharge and electron beam techniques. Commercial applications in some of these technologies have been developed, but there is considerable room for advancement. The same excitation techniques used in pollution remediation or control may also be applied to chemical processing or synthesis.
Among the technical disadvantages of existing approaches the following are noted. Thermal approaches alone are non-selective, and require large amounts of energy. Reactive chemical/catalytic approaches require purchased chemical reagents. For example, if ammonia is used as a reagent for the reduction of NO.sub.x in combustion exhaust, its use must be carefully monitored to avoid ammonia release, which could result in a secondary pollution problem. In catalytic methods, pollutants themselves or other chemical species or particulates contaminate and inactivate catalysts. Solid catalysts in particular become fouled and require replacement or regeneration. Non-thermal electric discharge/electron beam technologies directly excite all exposed species and, under particular conditions, are not adequately selective to modify the target contaminants in a useful manner. For example, in the single step removal of NO.sub.x from flue gas, nitric oxide in flue gas is rapidly converted into nitrogen and oxygen (desirable products) by nitrogen atoms generated in an electric discharge. However it is also rapidly converted into nitrogen dioxide or nitric acid and other oxidized species (undesirable products) by hydroxyl radicals in the same discharge. The nitric acid then requires additional treatment (e.g., chemical scrubbing) to remove it from the exhaust stream. In this example, achieving a single step NO removal process requires more control of the flue gas chemistry than is available by direct excitation of the flue gas. In some applications of control discharge technology, flue gases foul electrodes, which then require electrode cleaning or replacement. Further, the dielectric properties of materials used in barrier-type discharges are temperature dependent and thus add complexity to the design of such reactors used with the temperatures present in flue gas.